关于淀粉酶的叙述，错误的是（）。A．最适pH是6.7～7.0 B．可作用于淀粉的α-
题型：单项选择题
问题：
关于淀粉酶的叙述，错误的是（）。
A．最适pH是6.7～7.0
B．可作用于淀粉的α-1，4糖苷键和α-1，6糖苷键
C．是胰腺分泌的
D．是正常时唯一能在尿中出现的血浆酶
E．又称为胰酶
题型：单项选择题
| 根据短文内容，从方框内选择合适的单词并用其适当形式填空，使短文完整、连贯。 | |
 nd reading e-mail have become one of the most popular daily activities around the world, either for business or for pleasure. Now, more and more teachers and students are 1 this form (形式) of communication to 2 their language skills, particularly in English. E-mail has become so popular because it's quite 3 . In the past, teachers often 4 pen pal projects so that their students could 5 ideas with their pen pals. But sending and 6 paper letters could take a few weeks sometimes, so students might lose 7 in the project some day. Now with e-mail, __8__ , messages can be sent or received 9 on the Internet. 10 of waiting for days or weeks, students can receive a reply during days, hours, or even minutes. |